Science Service System

Summary of Proposal COA1536

TitleA comparative study of TerraSAR-X image characteristics over estuarine/coastal wetland for differentiating between annual and perennial halophyte species
Investigator Won, Joong-Sun - Yonsei University, Earth System Sciences
Team Member
Dr. Ryu, Joo-Hyung - Korea Institute of Ocean Science & Technology, Korea Ocean Satellite Center
Prof. Kim, Sang-Wan - Sejong University, Geoinformation Engineering
Prof. Jung, Hyung-Sup - University of Seoul, Geoinformatics
Dr. Hong, Sang-Hoon - Korea Aerospace Research Institute, Marine Geology and Geophysics
SummaryCoastal salt marsh is the dominant, mostly herbaceous vegetation of seacoast mudflats, especially outside the tropics and subtropics, including around estuaries and deltas. In tropical and subtropical latitudes, coastal salt marsh is instead mangrove vegetation. Annual plant over tidal flats and salt marsh is typically sensitive to local sea level, and migration of its habitats is an indicator of local sea level change. On the contrary, perennial halophytes are relatively stable in terms of plant structure and their distribution except seasonal variation of chlorophyll content. Thus it is very important to differentiate between annual and perennial halophyte species. While some independent studies on SAR signatures characterizing wetland vegetation such as mangrove have been made, a comparative study of X-band SAR signatures between salt marshes, tropical and delta swamp has rarely done. The main objective of the research is to define TerraSAR-X signatures according to mid latitude salt marshes, tropical mangrove swamp, and swamp developed at an estuary of large river systems for differentiating between annual and perennial halophyte species. The halophyte species and biophysical properties of the three types of wetlands are quite different and produce distinctive features of SAR signals.
To understand dynamic changes in coastal wetlands, both wetland vegetation and sedimentary process are needed to be studied. High resolution SAR is complementary to optical remote sensing in the coastal wetlands. Although radar signals are less sensitive to chlorophyll content, wetland vegetation in terms of plant structure as well as biophysical properties of bottom surface such as sediment grain size, surface water coverage, topography, channels and creeks, can be readily understood by SAR systems. In our previous research, it has been demonstrated that TerraSAR-X is potentially effective for discriminating and mapping different species, annual or perennial, of salt marsh vegetation and their seasonal variation. Main objectives of the research are application studies of TerraSAR-X on the coastal and inland wetland monitoring. To achieve the goals, investigations include: 1) detailed investigation of intertidal environment changes in terms of sedimentation/erosion trend, distribution of tidal channels and creeks, and migration of halophyte species; 2) backscattering and polarimetric signatures of wetland vegetation for classification; 3) potential mapping and change detection of mangrove forest in southern Mekong Delta; 4) calculating water balance of Tonle Sap Lake and Amazon River by estimating flow rate. Since TerraSAR-X has a capability of four different imaging modes, the effectiveness of each mode will also be investigated. There are huge archives over the study area and the high spatial/temporal resolution of TerraSAR-X will open a new perspective of wetland applications. The results are to be combined with those obtained by ENVISAT and ERS C-band data and ALOS L-band data. Main test sites are coastal areas of the Korean Peninsula and Mekong River including Tonle Sap Lake. Additional test site is Amazon River where mean flow rate is high and gauge information is available.
The west coast of the Korean Peninsula is proper for the main test site because of various tidal range (approximately 7.3 m at the north while approximately 3 m at the south) and various types of tidal flats (closed/semi-closed/open tidal flats). In addition, a large amount of field survey data such as the surface sediment type, leveling, surface roughness, depth of sedimentation, reflectance of tidal flats and tracking of the halophyte boundary, which would improve the coastal and inland wetland monitoring methods using TerraSAR-X, have been accumulated. The results will demonstrate a potential of space-borne high resolution X-band SAR systems for monitoring wetland vegetation and their changes.

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